1. Field of the Invention
The present invention relates to a semiconductor laser device suited for use in the field of optical logical operation and capable of high-speed modulations, a method of fabricating the same, and an optical system of utilizing the same.
2. Description of the Related Art
To realize a high speed semiconductor laser, it is indispensable to reduce parasitic capacitance. The semiconductor laser of the prior art of the type, in which the restriction of current is effected by burying with the p/n reverse junction, is troubled by a problem that the junction capacitance is dominantly large. As a method of reducing the parasitic capacitance of this buried heterostructure semiconductor laser (i.e., BH laser), it has been discussed by Matsumoto et al. on pp. 117 in Electron Lett. Vol. 24 (1988) that the buried semiconductor layer is partially removed from the outside of a radiative stripe. This semiconductor laser is shown in top plan view and in section, respectively, in FIGS. 2A and 2B. A p-InP buried layer 5 and an n-InP buried layer 6 are formed in the side of an active layer 3 of the mesa-stripe region which is composed of an optical guiding layer 2 and a cladding layer 4 in addition to the active layer 3. A p-electrode 8 formed over the n-InP buried layer 6 has its stripe-type electrode 8a with a width of 20 .mu.m and its pad electrode 8b with a restricted size of about 100 .mu.m in diameter to reduce the aforementioned p/n junction capacitance of the outside of the mesa-stripe.